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PP CFB toroidy OPT
PP CFB toroidy OPT
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Old 6th November 2018, 07:14 AM   #11
gregt is offline gregt  New Zealand
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See thread PP amp with Toriody Transformers and 7591A
Note that schematic changed on post 28. Samples of output into 8 ohms parrelled with 1uf. I like the look of your design...but I choose the 7591a tube as this is easier to drive given that the use of CFB the drive requirements double.
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Old 21st November 2018, 08:58 AM   #12
LKA is offline LKA  Europe
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I modified the driver circuit. Now, first stage is a triode loaded by CCS. Additional parameters are located on the schematic.
PP1-DRIVER-v2.3.JPG
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Old 22nd November 2018, 05:43 AM   #13
LKA is offline LKA  Europe
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some photos of assembled parts

PP1-AC-CTRL-front.jpg PP1-HDCPS-front.jpg PP1-HTPS-front.jpg PP1-HTPS-back.jpg
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Old 22nd November 2018, 07:31 AM   #14
gregt is offline gregt  New Zealand
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Very nice...great work
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Old 22nd November 2018, 07:43 AM   #15
LKA is offline LKA  Europe
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Thanks. In a few days OPS will be finished too. I'm currently working on driver pcb design, I hope I can send it to fabrication soon.
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Old 22nd November 2018, 10:29 AM   #16
artosalo is offline artosalo  Finland
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Why an non-linear component (1N4148) at the cathode of 1st. E88CC ?
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Old 22nd November 2018, 12:57 PM   #17
LKA is offline LKA  Europe
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Diode is optional, you can use resistor-resistor
D1 -> 470R
R5 -> 100R
R9,P6,C3 - according desired FB level

In my design (2xKT88 B+420V CFB Raa4K 40W/4R) OLG is 34dB and CLG 21dB. The driver required voltage swing is 140Vpp.
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Old 22nd November 2018, 06:34 PM   #18
gregt is offline gregt  New Zealand
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My understanding is that Toriodal transformers are more sensitive to DC imbalance in the output pair. John Broskie (Tubecad) proposed a Cross-Refenced Auto Bias Circuit in his thread "Blumleinís garter circuit revisited"

I will try this in my next design (also using Toriody transformers)
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Old 23rd November 2018, 02:31 PM   #19
LKA is offline LKA  Europe
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The finished output stage and associated high voltage power supply.

PP1-OPS-v1.4.JPG

PP1-OPS-front.jpg PP1-OPS-back.jpg PP1-OPS_PSU-1.jpg PP1-OPS_PSU-2.jpg
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Old 23rd November 2018, 02:53 PM   #20
Lingwendil is offline Lingwendil  United States
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PP CFB toroidy OPT
Quote:
Originally Posted by gregt View Post
My understanding is that Toriodal transformers are more sensitive to DC imbalance in the output pair. John Broskie (Tubecad) proposed a Cross-Refenced Auto Bias Circuit in his thread "Blumleinís garter circuit revisited"

I will try this in my next design (also using Toriody transformers)
Garter bias works very well, and I use it a great deal. I like it enough that my Flea amp uses it, and to be designing a PCB for it with EL84/86 types- 6N2P/6CW5 design with toroidal outputs
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